Carolina moonseed is a rather slender, twining vine with stems 16 feet long or more. It is scattered in southern and eastern Missouri. It bears clusters of bright red, somewhat flattened fruits. The disk-shaped seeds are spiraled like a snail shell.
Leaves are simple, alternate, blades 2–4 inches long and wide, broadly egg- to heart-shaped or often triangular, tip pointed to blunt or rounded, base flattened to heart-shaped, margin entire or shallowly 3- or 5-lobed, with 5 main veins from the base; upper surface paler, densely hairy; leaf stalk ¾–4 inches long, slender, hairy, occasionally sharply bent near the blade.
Stems are slender, twining, grayish green to grayish brown, hairy, tendrils absent.
Bark is pale grayish green to grayish brown, slightly grooved, the thin edges curled; old vines with ridges and warty spots of corky bark; wood soft, whitish, porous.
Flowers July–August, in loose clusters 1–6 inches long; flowers minute, yellowish green; petals 6, white; stamens 6, not extending beyond the petals; male and female flowers are found in separate clusters on the same plant, but in some cases the flowers may contain both sexes.
Fruits September–October, in grapelike clusters 1–6 inches long, rarely more than 2 inches wide; fruit brilliant red, very showy, glossy, smooth, globe-shaped, about ¼ inch across; seed creamy white, solitary, flattened, with the raised outer edge having a spiral pattern.
Similar species: Common moonseed is quite similar, but it has clusters of bluish-black (not bright red) berries, and the leaf stem attaches on the lower surface of the leaf blade (not to the edge of the leaf blade).
Catbrier (Smilax bona-nox) is a woody vine that has leaves with a rather similar shape, but its stems have tendrils as well as prickles; also, its leaves are more leathery.
Moonseeds may also be confused with our various species of wild grapes (Vitis spp.). Because wild grapes are edible and moonseeds are toxic if eaten, it is important to be able to distinguish between them. Key characters for identifying grapes are their toothed leaves, the curling tendrils by which they climb, and their seeds, which are not disk-shaped or bowl-shaped.